Two major goals of neuroscience research are (1) to understand how sensory information guides behavior and (2) to understand how behaviors are modified by experience. In most sensory modalities, extracting salient information involves passing signals back-and-forth between multiple, highly-interconnected neural circuits, making it challenging to disentangle which computations are made by which neuronal populations. For this reason, there is a significant advantage to studying sensory processing in neural pathways that involve few interconnected circuits. In mice, a specialized chemosensory pathway called the accessory olfactory system strongly influences social behavior and utilizes just one small neural circuit for the majority of its information processing. This small neural circuit is called the accessory olfactory bulb (AOB), and the proposed research aims to determine how neurons in the AOB extract behaviorally-relevant chemosensory information from the environment and refine that information through experience. Information processing in the AOB critically depends on the function of several classes of inhibitory interneurons, and neural plasticity in AOB interneurons is thought to underlie forms of social learning. The proposed research will use electrophysiology, neuronal calcium imaging, and optogenetics to determine the specific sensory computations performed by three major classes of AOB interneurons. The proposal leverages a unique ex vivo preparation of the AOB that allows researchers to monitor and manipulate AOB neurons during naturalistic peripheral chemosensory stimulation, which is important for relating activity measurements to information content. Furthermore, the proposed experiments will determine how the computations made by these interneurons contribute to the expression of social behaviors. The final proposed experiments will investigate how experience-dependent plasticity in one of the AOB interneuron classes impacts forms of social learning. Overall, the proposed research will produce important insights into the neural mechanisms of sensory processing, social behaviors, and behavioral plasticity.